Tile Adhesive Calculator
Notch depth drives the quantity: about 1.6 kg/m² per mm.
Inputs
Result
Formula
| Base ≈ notch (mm) × 1.6 | kg/m² |
| Actual = base × back-buttering × flatness | |
| Total = actual × area | |
| Bags = ceil(total ÷ bag size) |
50 m² of floor with 600×600 tiles on an 8 mm notch, no back buttering, flat base: 12.8 kg/m², 640 kg total, 32 bags of 20 kg. Adding back buttering (as large format requires) with the same notch raises it to 20.5 kg/m² and 52 bags.
FAQ
Why is the ratio not one to one?
A notch trowel leaves ridges separated by voids that must be filled when the tile is bedded. Ideally the ridges occupy half the volume, which is why an 8 mm notch uses about 12.8 kg/m² rather than a solid 12 kg. Notch shape, trowel angle and bedding pressure all change coverage - hence the requirement to lift a tile and check, not just eyeball the comb.
Why must large format tiles be back buttered?
They are stiff and heavy, so they cannot conform to the substrate the way small tiles do, and air trapped between the ridges cannot escape, leaving voids. Back buttering pushes the air out and raises contact area. Codes require two-sided application for tiles above 900×900 and for external thin-bed work. Without it, hollow spots and detachment are likely within a year or two.
Can cement be added to tile adhesive?
Never. Tile adhesive is a factory blend of cement with redispersible polymer and cellulose ethers; adding cement destroys the flexible polymer network, cutting bond strength and causing shrinkage cracks. Nor should sand be added, or water to a mix that has begun to set. Many hollow-tile failures trace to exactly this, and nothing shows until inspection.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.